Transfer device for a four-wheel drive motor vehicle

Abstract

A transfer device is provided for distributing the output of a transmission to front wheels and rear-wheels through a front power train and a rear power train. The output shaft of the transmission is operatively connected to the rear power train. The transfer device has a drive gear rotatably mounted on the output shaft of the transmission and engaged with a driven gear in the front power train, a fluid operated multiple-disk friction clutch having a drive drum and a driven drum. The driven drum is secured to the drive gear and the drive drum is secured to the output shaft. A piston is slidably mounted in a piston chamber and operated by oil supplied to the piston chamber for engaging the drive drum with the driven drum. A centifugal force oil chamber is formed in the fluid operated clutch opposite to the piston chamber, interposing the piston. The oil chamber is supplied with oil through an oil supply passage. A connecting passage is provided for connecting the centrifugal force oil chamber with the oil supply passage, and a check valve is provided in the connecting passage so as to maintain oil in the centrifugal force oil chamber. Thus, centrifugal force of the oil in the oil chamber acts on the piston to release the clutch.

What is claimed is: 
     
       1. A transfer device for a four-wheel drive motor vehicle for transmitting output of a transmission and for distributing the output to front wheels and rear wheels through a front power train and a rear power train, comprising; a fluid operated clutch having a drive drum and a driven drum which are engaged with each other by pressurized oil, the drive drum being secured to the output shaft of the transmission and to one of the front and rear power trains and the driven drum being secured to the other power train, and a piston slidably mounted in a piston chamber and operated by oil supplied to the piston chamber for engaging the drive drum with the driven drum;   a centrifugal force oil chamber formed in the fluid operated clutch opposite to the piston chamber, interposing the piston;   an oil supply passage for supplying oil in the piston chamber and for operating the piston;   a spring provided in the centrifugal force oil chamber for urging the piston in a releasing direction;   a connecting passage connecting the centrifugal force oil chamber with the oil supply passage;   a check valve provided in the connecting passage so as to maintain oil in the centrifugal force oil chamber, whereby centrifugal force of the oil in the oil chamber acts on the piston to release the clutch.   
     
     
       2. The system according to claim 1 wherein the transmission is an automatic transmission. 
     
     
       3. The system according to claim 1 wherein the fluid operated clutch is a fluid operated multiple-disk friction clutch.